Jones D K, Horsfield M A, Simmons A
Division of Medical Physics, University of Leicester, Leicester Royal Infirmary, Leicester LE1 5WW, United Kingdom.
Magn Reson Med. 1999 Sep;42(3):515-25.
The optimization of acquisition parameters for precise measurement of diffusion in anisotropic systems is described. First, an algorithm is presented that minimizes the bias inherent in making measurements with a fixed set of gradient vector directions by spreading out measurements in 3-dimensional gradient vector space. Next, it is shown how the set of b-matrices and echo time can be optimized for estimating the diffusion tensor and its scalar invariants. The standard deviation in the estimate of the tensor trace in a water phantom was reduced by more than 40% and the artefactual anisotropy was reduced by more than 60% when using the optimized scheme compared with a more conventional scheme for the same scan time, and marked improvements are demonstrated in the human brain with the optimized sequences. Use of these optimal schemes results in reduced scan times, increased precision, or improved resolution in diffusion tensor images. Magn Reson Med 42:515-525, 1999.
本文描述了用于在各向异性系统中精确测量扩散的采集参数优化方法。首先，提出了一种算法，该算法通过在三维梯度向量空间中分散测量来最小化使用固定梯度向量方向集进行测量时固有的偏差。接下来，展示了如何优化b矩阵集和回波时间以估计扩散张量及其标量不变量。与相同扫描时间下的更传统方案相比，使用优化方案时，水模中张量迹估计的标准偏差降低了40%以上，伪各向异性降低了60%以上，并且在人脑成像中使用优化序列也显示出显著改善。使用这些优化方案可减少扩散张量图像的扫描时间、提高精度或改善分辨率。《磁共振医学》42:515 - 525, 1999年。
